Editors' ChoicePhysiology

Detecting Injury to Infer Predators

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Science Signaling  27 Mar 2012:
Vol. 5, Issue 217, pp. ec92
DOI: 10.1126/scisignal.2003071

Many species react with fear to the presence of an injured member of the same species (see Stensmyr and Maderspacher). Mathuru et al. used biochemical techniques to isolate the component of a high-molecular-weight (~30 kD) fraction from zebrafish skin extract that elicited fear behaviors (slow swimming and descent to the bottom of the tank) in zebrafish. Noting that not only would skin extract cause fear behavior but that mucous released by sloughing from fish subjected to shaking also caused the behaviors, the authors used biochemical analysis to show that fish skin extract contained glycosaminoglycans (GAGs)—in particular, nonsulfated chondroitin, chondroitin-4-sulfate, and chondroitin-6-sulfate. Immunodepletion of chondroitins from the slough samples eliminated the induced fear behaviors. Using commercially available chondroitin preparations, the authors determined that chondroitin-6-sulfate or a mix of chondroitin-6-sulfate and chondroitin-4-sulfate triggered fear behaviors. In transgenic fish expressing a calcium indicator protein, exposure to skin extract triggered activity of the olfactory bulb in three distinct locations. The high-molecular-weight fraction of skin extract and chondroitin sulfate purified from shark cartilage consistently activated a particular one of these olfactory bulb regions, the mediodorsal locus. Thus, chondroitin sulfate released from mucous and skin from injured fish allows conspecific fish to react to the inferred threat with a fear response.

A. S. Mathuru, C. Kibat, W. F. Cheong, G. Shui, M. R. Wenk, R. W. Friedrich, S. Jesuthasan, Chondroitin fragments are odorants that trigger fear behavior in fish. Curr. Biol. 22, 538–544 (2012). [Online Journal]

M. C. Stensmyr, F. Maderspacher, Pheromones: Fish fear factor. Curr. Biol. 22, R183–R186 (2012). [Online Journal]

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